1. Field of the Invention
The present invention relates to a search system for searching for the information of a document, etc. by combining a plurality of search conditions, and a method thereof.
2. Description of the Related Art
A full text search system is used to extract a text including a target keyword from a large volume of text data. Examples of application fields include an Internet search, a patent search, a document search by groupware, a document search in a library, etc.
The full text search system holds document information to be searched as a text database in a form referred to as an inverted index. When a search expression where a plurality of keywords are combined by a logical operator such as “AND” or “OR” is provided as an input, the number of documents and a list of (the names or the IDs of) the documents which satisfy the condition represented by the search expression, are returned as search results. P If keywords are combined by “AND”, a document including both of the combined keywords is returned. If keywords are combined by “OR”, a document including at least either of the keywords is returned. Additionally, a related word which frequently appears along with a keyword included in an input search expression can be returned depending on a system.
FIG. 1A shows such a full text search system. The system shown in FIG. 1A comprises a text database 1 and a full text search engine 2. Assuming that a search expression “TOKYO AND SUBWAY” is input, the search engine 2 searches the text database 1 for a document including both of the keywords “TOKYO” and “SUBWAY”, and outputs a search result. Here, the number of hit documents, the IDs of the hit documents, and words related to the keywords are output.
FIG. 1B shows a typical user interface for inputs/outputs in the full text search system shown in FIG. 1A. On a search condition input screen 3, a database to be searched can be selected from three databases DB1, DB2, and DB3, and a search expression of keywords (Keywords) and duration to be searched (DATE) can be specified. The duration to be searched indicates the range of the dates written in documents.
In this example, DB2 is selected as a database to be searched, “TOKYO AND SUBWAY” is specified as a search expression, and the dates from Oct. 21, 1995 till Jun. 1, 1996 are specified as duration to be searched.
When a user presses (clicks with a pointing device) a Search button 4 after setting these search conditions, a search process starts to be executed. On a search result output screen 5, the number of documents found as a result of the search and the list of the documents are displayed. In this example, the finding of 4 documents, the list of the IDs of the documents (DocID), and their titles (Title) are displayed.
Furthermore, on a related word output screen 6, a list of keywords related to search conditions is displayed. In this example, keywords such as “Marunouchi-line”, etc. are displayed as related words.
However, the above described conventional full text search system has the following problems.
With a conventional user interface, the number of search condition combinations that can be issued at one time is only one. If a search result change is desired to be examined by slightly changing respective search conditions, a search must be repeated the number of times, which is equal to the number of combinations of different search conditions.
For example, if a search is desired to be performed with the search expression “TOKYO AND SUBWAY” by dividing the duration from 1992 till 1998 in year units, a search must be repeated 7 times while changing the condition of the duration to be searched. Accordingly, a heavy workload of inputting the search conditions is imposed, which leads to system operability difficulties for the user.
Furthermore, since search results output for a plurality of search condition combinations are displayed for the respective combinations, it is difficult to arrange and compare the results. As a result, a search result change when a search condition is slightly changed cannot be recognized inclusively.